1. Field of the Invention
The present invention relates to virtualization server technology, and more particularly to managing virtual hard drives (VHDs) of logical servers and corresponding VHD component files.
2. Description of the Related Art
There are many situations in which it is desired to lease one or more server computer systems on a short or long-term basis. Examples include educational or classroom services, demonstration of software to potential users or buyers, website server applications, etc. The servers may be pre-configured with selected operating systems and application software as desired. Although physical servers may be leased and physically delivered for onsite use, servers may also be leased from a central or remote location and accessed via an intermediate network system, such as the Internet. The primary considerations for remote access include the capabilities of the remote access software and the network connection or interface.
Virtualization technology enabled multiple logical servers to operate on a single physical computer. Previously, logical servers were tied directly to physical servers because they relied on the physical server's attributes and resources for their identity. Virtualization technology weakened this restriction by allowing multiple logical servers to override a physical server's attributes and share its resources. Each logical server is operated substantially independent of other logical servers and provides virtual isolation among users effectively partitioning a physical server into multiple logical servers.
A prior disclosure introduced virtualization that enabled complete separation between logical and physical servers so that a logical server may exist independent of a specific physical server. The logical server cloud virtualization added a layer of abstraction and redirection between logical and physical servers. Logical servers were implemented to exist as logical entities that were decoupled from physical server resources that instantiated the logical server. Decoupling meant that the logical attributes of a logical server were non-deterministically allocated to physical resources, thereby effectively creating a cloud of logical servers over one or more physical servers. The prior disclosure described a new deployment architecture which applied theoretical treatment of servers as logical resources in order to create a logical server cloud. Complete logical separation was facilitated by the addition of the SCM, which is an automated multi-server management layer. A fundamental aspect to a logical server cloud is that the user does not have to know or provide any physical server information to access one or more logical server(s), since this information is maintained within the SCM. Each logical server is substantially accessed in the same manner regardless of underlying physical servers. The user experiences no change in access approach even when a logical server is reallocated to a different physical server. Any such reallocation can be completely transparent to the user.
A second prior disclosure built upon logical server cloud virtualization by adding a layer of abstraction and redirection between logical servers and the server clouds as managed and controlled by corresponding SCMs. The server cloud was accessed via its SCM by a user via a user interface for accessing logical and physical servers and by the logical and physical servers themselves, such as via logical and/or physical agents as previously described. SCMs interfaced each other according to predetermined relationships or protocols, such as “peer” SCMs or server clouds or between a server cloud and a “super peer”, otherwise referred to as an “Exchange”. The second disclosure introduced the concept of a “subcloud” in which an SCM interfaced or communicated with one or more logical and/or physical servers of another server cloud. The SCM of the server cloud operated as an intermediary or proxy for enabling communication between a logical server deployed within a remote cloud. Logical servers could be moved from one server cloud to another or replicated between clouds. A remote SCM could manage one or more logical servers in a subcloud of a remote server cloud. In fact, a logical server might not be aware that it was in a remote cloud and may have behaved as though it resided in the same cloud as the SCM managing its operations. The proxy functionality enabled transparency between users and logical servers. The user of a logical server may or may not be aware of where the logical server existed or in which server cloud it is instantiated.
Many advantages and capabilities were enabled with cloud to cloud interfacing. Routing, switching, replication and cloud balancing may be performed intercloud, such as between “trusted” clouds, extracloud, such as between “untrusted” clouds, or via an intermediary (e.g., super-peer, supercloud, shared storage, exchange) in which actions requested of one SCM were transparently performed by a different SCM. An exchange cloud could be established that had predetermined commercial relationships with other clouds or that was capable of querying public or otherwise accessible clouds for resource information. Such an exchange cloud could be established on a commercial basis, for example, to provide a free market exchange for servers or services related thereto. Exchange clouds included intercloud proxy and predetermined business rules and relationships to conduct commercial transactions. Such commercial transactions might include, for example, sale or lease of logical servers on the market through a common exchange and medium, such as the Internet.
Multiple logical servers may be defined and use of logical servers may facilitate creation of additional logical servers based on usage. Each logical server may be represented as a series of components, where each component may further be represented as a chain of one or more files. The integrity of each server is integrally linked to the integrity of the chain of files used to comprise the server. Modification to any parent file in any chain effectively eliminates the validity of subsequent files or file sets. A significant challenge exists to manage server component files in a system comprising multiple logical servers with many possible combinations of file relationships between component files.